In the following, an actuator device with a processing unit for use in a land vehicle is described, wherein the actuator device is connected to a main control unit contained in the land vehicle.
Actuator devices are frequently used in modern land vehicles. In this case a processing unit is normally provided, which is subordinate to a main control unit. The main control unit is designed to transmit control commands, for example actuator setting commands, to the processing unit. The processing unit receives the control commands from the main control unit and is provided to control the actuator according to the commands transmitted by the main control unit. In this case the main control unit acts as a master unit and the processing unit serves as a slave unit. Such a concept makes it possible for example to arrange power electronics for operating the actuator spatially separated from the main control unit. The communication between the main control unit and the processing unit normally takes place via a data bus. In the case of land vehicles, such a bus is often a LIN bus, a CAN bus or a FlexRay bus.
An electronic control system for a vehicle braking system is known from DE 101 18 263 A1, and corresponding US patent publication No. 2004/015281, the US document being incorporated by reference herein. The control system has a fault-tolerant driver input module for recording driver braking input and two brake circuit modules for controlling the wheel brakes. Assigned to each brake circuit module is an electrically controllable brake actuator, assigned to which structurally and logically is a local electronic unit for executing actuator-specific control functions and/or sensor-specific evaluation functions, which unit is connected via a local brake circuit data bus to the brake circuit module of the respective brake circuit. The sensor signals of each respective actuator and the at least one wheel, to which the actuator applies a braking force, are recorded by the local electronic unit and made available as digital signals to the brake module via the brake circuit data bus. The brake actuators of one brake circuit are electromechanical actuators with an electronically commutated motor, the commutation of the motor being carried out in the local electronic unit. The local electronic units and the assigned sensors are supplied with electrical energy via the brake circuit data bus or its physical medium. The brake circuit modules are connected via a fault-tolerant communications system to one another, to the driver input module and to an optionally present control module for calculating primary brake regulating functions. The control modules of the vehicle braking system are connected to control modules of additional electronic control systems via a fault-tolerant communications system, which is designed as a vehicle data bus. In the driver input module, in addition to the service brake input or parking brake input, the steering input, driving position selection or the propulsive power input is recorded and transmitted via the communications system to the corresponding control module for making a setting. In the driving dynamics module, in the event of situations that are critical from a driving dynamics point of view, a modification of the driver steering input is undertaken while convenience functions such as a variable steering ratio are displayed.
From DE 198 54 788 A1, and corresponding U.S. Pat. No. 6,216,080 B1, the US document being incorporated by reference herein, a wheel module for a vehicle with an electrically controllable braking system for the control of the braking force on at least one wheel of the vehicle is known. A brake value indicating the desired target braking force for the wheel, a wheel-specific signal of the wheel and an additional wheel-specific signal of an additional wheel are supplied to the wheel module. The wheel module emits an adjusting signal calculated using the brake value and the wheel-specific signals to an actuator. The actuator serves to adjust the braking force on the wheel. Assigned to the wheel are a main regulating channel and an additional regulating channel. Wheel-specific computing steps are executed in each case in both regulating channels. The adjusting signal is computed in the main regulating channel using computing results of the additional regulating channel. The wheel-specific signal of the wheel is supplied to the wheel module at a higher repetition frequency than the additional wheel-specific signal of the additional wheel. A signal indicating the rotational speed of the wheel is used as a wheel-specific signal. The wheel-specific computing steps contain computing steps for an anti-lock regulation of a wheel, in which intermediate results are formed, and the adjusting signal is calculated by using the intermediate results. A central module is used for central execution of vehicle-wide brake control functions, the central module being connected to the wheel modules via one or more data bus systems for the exchange of information.
An electronic brake system for road vehicles with an electronic device that serves to control brake-pressure modulators is known from DE 40 22 671 A1, and corresponding U.S. Pat. No. 5,255,962 A, the US document being incorporated by reference herein. The electronic device is divided up into several wheel modules with their own intelligence that are assigned to the wheels and provided with at least one microcomputer, the wheel modules being arranged spatially in the vicinity of the wheels. A superior central module provided with a microcomputer has its own intelligence and is arranged in a central location of the vehicle. The central module receives the values of an operating brake-value transmitter and a parking brake. The wheel modules receive a brake pressure reference value from the central module. The wheel modules receive measured values for the wheel speed and the brake pressure from sensors on the related wheel or brake cylinder or brake-pressure modulator. The wheel modules transmit at least one of the measured values they receive and information derived therefrom respectively to the central module. The wheel modules generate electric output signals to control a related brake-pressure modulator that is preferably structurally combined with the wheel modules. The information exchange between the central module and the wheel modules takes place via at least one data bus with fixed interfaces. A brake pressure modification and subdivision respectively are performed in the central modules according to load criteria and/or brake lining wear criteria. An antilock and/or antiskid function is contained in the wheel modules. A vehicle reference speed for the antilock function is formed in the central module. In the event of a disturbance, the power supply to the wheel modules can be switched off by the central module by means of electronic switches or relays. The data buses are formed as optical fibres. The wheel modules receive information about brake lining thicknesses and temperatures via additional input lines. Two wheel modules can be combined to form one axle module.
DE 43 39 570 A1, and corresponding U.S. Pat. No. 5,752,748 A, the US document being incorporated by reference herein, show an electronic brake system in which an intelligent central module and intelligent brake modules assigned to the wheels or wheel groups are provided. The brake modules are connected to the central module via a communications system and send sensor signals to the central module and receive brake pressure nominal values from the central module. The brake modules control the nominal brake pressures by means of electrically operable actuators assigned to the wheels depending on the brake pedal input requirement at the wheels. The brake pedal is additionally formed as a pressure generator and is connectable to the brakes of a brake circuit via a switch unit. The brake pedal sensor is connected to a brake module to route the sensor value to the central module and to calculate the nominal brake pressures for all wheels if the central module fails and to route these to the corresponding brake modules via the communications system. If the brake module fails, this connection is made.
The brake module connected to the pedal sensor is assigned to the brake circuit, which is connectable to the pressure generator operated by the brake pedal. The brake circuit connectable to the pressure generator operable by the brake pedal is the front axle brake circuit. The brake circuit is connected to the pressure generator operable by the brake pedal if faulty pedal sensor signals occur.
A braking system for a motor vehicle is known from DE 196 15 186 C1, and corresponding U.S. Pat. No. 6,030,054 A, the US document being incorporated by reference herein, with an actuating device, which is formed as an electromechanical wheel brake actuator mounted on the brake calliper of a wheel, which actuator contains a spindle driven by an electric motor in an axial direction. The electric motor has a rotor, which is formed as a spindle nut of a spindle gear converting its rotary movement into a linear movement of the spindle. The axial force of the spindle is multiplied by a mechanical transmission and transmitted to a piston of a wheel brake cylinder to press brake linings onto a brake disc. Rotor magnets of the electric motor are fitted on the spindle nut. The wheel brake actuator with spindle gear is used as a parking brake. Control electronics are integrated into the housing of the wheel brake actuator.
Such actuators can be used in land vehicles in particular for safety-relevant systems, such as electronically controllable parking brake systems. Problems can occur, however, if incorrect signals are transmitted via the bus. If safety-relevant systems are affected by such a fault, significant consequences can result for vehicle safety. For example, in the case of a parking brake, the parking brake can be released in an uncontrolled manner on a slope due to an incorrect signal or can lead during travel to unexpected and undesired braking. Both can have a substantial adverse effect on the safety of the driver and the passengers in a vehicle as well as on other road users.
The object is to provide an actuator device for which system reliability is guaranteed even in the event of such a fault being present, so as not to jeopardize vehicle occupants as well as other road users unnecessarily.